Effects of hyperbaric oxygen combined cabin ventilator on critically ill patients with liberation difficulty after tracheostomy

Background Critically ill patients undergoing liberation often encounter various physiological and clinical complexities and challenges. However, whether the combination of hyperbaric oxygen and in-cabin ventilator therapy could offer a comprehensive approach that may simultaneously address respiratory and potentially improve outcomes in this challenging patient population remain unclear. Methods This retrospective study involved 148 patients experiencing difficulty in liberation after tracheotomy. Inclusion criteria comprised ongoing mechanical ventilation need, lung inflammation on computed tomography (CT) scans, and Glasgow Coma Scale (GCS) scores of ≤ 9. Exclusion criteria excluded patients with active bleeding, untreated pneumothorax, cerebrospinal fluid leakage, and a heart rate below 50 beats per minute. Following exclusions, 111 cases were treated with hyperbaric oxygen combined cabin ventilator, of which 72 cases were successfully liberated (SL group) and 28 cases (NSL group) were not successfully liberated. The hyperbaric oxygen chamber group received pressurization to 0.20 MPa (2.0 ATA) for 20 min, followed by 60 min of ventilator oxygen inhalation. Successful liberation was determined by a strict process, including subjective and objective criteria, with a prolonged spontaneous breathing trial. GCS assessments were conducted to evaluate consciousness levels, with scores categorized as normal, mildly impaired, moderately impaired, or severely impaired. Results Patients who underwent treatment exhibited improved GCS, blood gas indicators, and cardiac function indexes. The improvement of GCS, partial pressure of oxygen (PaO2), oxygen saturation of blood (SaO2), oxygenation index (OI) in the SL group was significantly higher than that of the NSL group. However, there was no significant difference in the improvement of left ventricular ejection fraction (LVEF), left ventricular end-systolic volume (LVESV), left ventricular end-diastolic volume (LVEDV), and stroke volume (SV) between the SL group and the NSL group after treatment. Conclusions Hyperbaric oxygen combined with in-cabin ventilator therapy effectively enhances respiratory function, cardiopulmonary function, and various indicators of critically ill patients with liberation difficulty after tracheostomy. Supplementary Information The online version contains supplementary material available at 10.1186/s12938-024-01220-4.


Introduction
Mechanical ventilation stands as a prevalent supportive intervention for critically ill patients within the confines of the Intensive Care Unit (ICU).This method serves to rectify or mitigate acute and chronic respiratory failure stemming from diverse etiologies [1].Nevertheless, prolonged reliance on mechanical ventilation may inflict harm upon the upper respiratory tract or induce the diaphragm atrophy.This, in turn, precipitates adverse consequences such as ventilator-associated diaphragmatic dysfunction, posing challenges to the liberation process [2].Moreover, protracted tracheal intubation during mechanical ventilation heightens the susceptibility to pulmonary infections and exacerbates organ impairments [3].Clinical investigations have additionally discerned that extended ventilator use hampers blood circulation in immobilized patients, fostering thrombosis and engendering pulmonary embolism [4].Therefore, as the primary disease improves, respiratory failure is corrected, and spontaneous breathing is restored, patients should start liberation as soon as possible [5].Delayed liberation will increase the complications of mechanical ventilation (pneumonia, airway injury, etc.), hospital stay and medical treatment cost [6].
Concomitantly, with the advancement of rigorous rehabilitation practices, the clinical efficacy of hyperbaric oxygen therapy in conditions like brain trauma, cerebral hemorrhage, and hypoxic-ischemic encephalopathy has garnered empirical confirmation [7][8][9].Hyperbaric oxygen therapy involves breathing pure oxygen in a pressurized room or chamber [9].This treatment boosts the amount of oxygen the blood can carry, promoting faster healing and reducing inflammation [10].In addition, studies have shown that hyperbaric oxygen can increase the body's blood oxygen partial pressure, improve myocardial microcirculation, increase myocardial contractility, and increase cardiac ejection fraction [11].
To address the challenges of long-term mechanical ventilation liberation, clinical interventions typically focus on the reasons for liberation failure [12].Some main factors contributing to liberation difficulties include inadequate control of the primary disease, poor nutritional status among long-term ventilator-dependent patients, and erroneous judgment by doctors, leading to difficulties in the liberation process [13][14][15].In view of the reasons for the difficulty of liberation, conventional interventions can improve the patient's condition by controlling the primary disease, correcting the nutritional status, psychological intervention and choosing the right time for liberation [16].However, a large number of practices have also shown that conventional intervention methods are not satisfactory for some patients.Therefore, in order to improve the success rate of liberation, more effective intervention methods are advocated [17].Therefore, we hypothesize that the combination of hyperbaric oxygen and in-cabin ventilator therapy may have benefits for critically ill patients with liberation difficulty after tracheostomy.

Demographic and clinical characteristics of the study subjects
The flowchart of the study is shown in Fig. 1.In this study, 148 patients with difficulty in liberation (after tracheotomy) were initially selected as the research subjects and were assessed for eligibility.Next, 37 patients were excluded, including those who did not meet the inclusion criteria and (n = 25) and those who declined to participate (n = 12).The remaining 111 patients were treated with hyperbaric oxygen combined with incabin ventilator therapy.Subsequently, 11 patients were excluded, including those who transferred to another hospital (n = 4), withdrew (n = 2), and died (n = 5).Finally, 72 cases were successfully liberated and 28 cases were unsuccessful liberated, and they were devoted into two groups and used for comparative analysis.Table 1 shows the demographic characteristics, primary disease status, and the statistics of the number of invasive ventilators in the hyperbaric combined cabin between the successfully liberated patients (SL group) and the unsuccessful liberation patients (NSL group).The average age of the SL group was 71.2 ± 8.8.The average age of the NSL group was 73.5 ± 9.4.Primary diseases include hypoxic-ischemic encephalopathy, respiratory failure, cerebral trauma, cerebral hemorrhage, carbon monoxide poisoning, and spinal cord injury.There was no significant difference between gender (p = 0.643), age (p = 0.118), mechanical ventilation duration (p = 0.336) and primary diseases (p = 0.355) between two groups.However, according to the ventilator liberation procedure, the number of invasive ventilators in hyperbaric oxygen combined cabin was significantly different between the two groups (p = 0.029).

Glasgow Coma Scale (GCS) scores in the NSL and SL group
Our research findings revealed no statistically significant difference in GCS scores between the NSL and SL groups prior to treatment (p > 0.05, as illustrated in Fig. 2).However, following the administration of hyperbaric oxygen in conjunction with incabin ventilator therapy, both the SL and NSL groups exhibited noteworthy enhancements in GCS scores (p < 0.0001).Notably, the magnitude of improvement in GCS scores was significantly greater in the SL group compared to the NSL group (p = 0.0015).the NSL and SL groups before treatment (p > 0.05, Fig. 3A-C).However, after administering hyperbaric oxygen combined with in-cabin ventilator therapy, both the SL and NSL groups demonstrated significant improvements in PaO2 (Fig. 3A), SaO2 (Fig. 3B), and OI (Fig. 3C).Notably, the improvements were significantly higher in the SL group compared to the NSL group (p < 0.0001).Additional file 1: Figure S2 provides a comparison of blood gas analysis for all patients before and after treatment.Overall, the PaO2, SaO2, and OI levels in patients showed significant increases after treatment (p < 0.0001), indicating that hyperbaric oxygen combined with in-cabin ventilator therapy effectively improved blood gas indicators in patients.

Cardiac function indexes in the NSL and SL group
We then examined the changes in cardiac function indexes between the SL group and the NSL group.Although cardiac function is not typically used as a parameter for liberation, it still could be a potential limitation for successful liberation.Our findings revealed no significant difference in left ventricular ejection fraction (LVEF), left ventricular end-systolic volume (LVESV), left ventricular end-diastolic volume (LVEDV), and stroke volume (SV) between the NSL and SL groups before treatment (p > 0.05, Fig. 4A-D).However, after administering hyperbaric oxygen combined with in-cabin ventilator therapy, both the SL and NSL groups exhibited significant improvements in LVEF (Fig. 4A), LVESV (Fig. 4B), LVEDV (Fig. 4C), and SV (Fig. 4D).Nonetheless, there were no significant differences in the degree of improvement in these various cardiac function indexes between the SL and NSL groups after treatment (p > 0.05, Fig. 4A-D).
Additional file 1: Figure S3 provides a comparison of the changes in cardiac function for all patients before and after treatment.Overall, patients showed significant increases in LVEF, LVESV, LVEDV, and SV after treatment (p < 0.0001), indicating that hyperbaric oxygen combined with in-cabin ventilator therapy has a significant positive impact on improving heart function indicators.

Discussion
While mechanical ventilation plays a crucial role in emergency resuscitation and the care of critically ill patients, liberated patients off the ventilator poses a significant challenge for physicians [18].Early initiation and prompt liberation are generally recommended for mechanically ventilated patients.However, difficulties in liberation can lead to complications, impair respiratory function, and increase the financial burden on patients [19].At present, hyperbaric oxygen therapy has been widely used in the treatment of cerebrovascular diseases and other diseases [20].Early implementation of hyperbaric oxygen therapy promotes the growth rate of nerve cell axons, facilitates the development of collateral cerebral circulation, enhances compensation and reorganization of healthy brain cells or tissues around the lesion, improves brain plasticity, and supports effective recovery of brain function [21].Administering in-cabin hyperbaric oxygen treatment promptly not only improves hypoxia and reduces intracranial pressure, but also mitigates nerve cell apoptosis and lowers the disability rate [22].The application of an in-cabin ventilator, in conjunction with hyperbaric oxygen therapy, ensures patients can maintain stable physical signs within the unique hyperbaric oxygen environment.It also provides auxiliary support for successful liberation [22].
The study began with 148 patients facing challenges in liberation after tracheotomy, ultimately resulting in 72 successfully liberated cases and 28 unsuccessful cases.A comprehensive analysis of demographic characteristics, primary disease status, and the number of invasive ventilators revealed no significant differences in gender, age, mechanical ventilation duration, and primary diseases between the SL and NSL groups.However, the number of invasive ventilators in the hyperbaric oxygen combined cabin was notably different between the two groups (p = 0.029).This result indicates that too many times of invasive ventilator may prevent successful liberation of the patients treated with hyperbaric oxygen.Prior to treatment, there were Fig. 4 Comparisons of the LVEF (A), LVESV (B), LVEDV (C) and SV (D) between the two groups before and after hyperbaric oxygen combined cabin ventilator treatment.Data were presented as mean ± SD showing all the data points.***p < 0.001 and ns means no significance.Two-way ANOVA followed Turkey's multiple comparisons test no significant differences in GCS scores between the NSL and SL groups.Following hyperbaric oxygen therapy combined with in-cabin ventilator therapy, both groups exhibited substantial improvements in GCS scores, with the SL group demonstrating a significantly greater enhancement compared to the NSL group (p = 0.0015).This outcome underscores the efficacy of the combined therapy in enhancing neurological outcomes, with clinical implications for patients undergoing liberation difficulties after tracheotomy.
Blood gas analysis indicators, including PaO2, SaO2, and OI, demonstrated no significant differences between the NSL and SL groups before treatment.However, post-treatment, both groups exhibited significant improvements in these indicators, with the SL group showing significantly greater enhancement.This suggests that hyperbaric oxygen combined with in-cabin ventilator therapy effectively improved blood gas parameters, highlighting its clinical utility in optimizing oxygenation in patients with liberation difficulties.Initial assessments revealed no significant differences in cardiac function indexes between the NSL and SL groups.After treatment, both groups exhibited significant improvements in LVEF, LVESV, LVEDV, and SV.Importantly, no significant differences were observed in the degree of improvement between the two groups.These results indicate a positive impact of hyperbaric oxygen combined with in-cabin ventilator therapy on cardiac function, emphasizing its potential benefits in enhancing heart function indicators.
Indeed, there are certain limitations of the study.The study included a total of 111 patients after exclusion criteria, which may be considered a relatively small sample size.The results could be due to significant bias.A larger sample size would provide more robust statistical power and increase the generalizability of the findings.Secondly, the study selected patients from a specific hospital, which may introduce selection bias and limit the generalizability of the results to other settings or patient populations.The inclusion criteria and exclusion criteria used in the study may have also influenced the characteristics of the patient sample.Thirdly, the study primarily focuses on the effects of hyperbaric oxygen combined with in-cabin ventilator therapy on liberation difficulty.However, there is no mention of long-term followup to assess the durability of the observed outcomes or the potential for relapse after treatment.In addition, the main reason for patients' improvement in GCS is symptomatic surgery and treatment, and hyperbaric oxygen may be only a small reason.Since our study is a retrospective study, we can no longer compare the GCS of patients treated with hyperbaric oxygen and those without treatment.

Conclusion
In summary, the comprehensive analysis of the study results supports the clinical use of hyperbaric oxygen therapy combined with in-cabin mechanical ventilation in patients facing liberation difficulties after tracheotomy.The combined therapy demonstrates positive effects on neurological outcomes, blood gas parameters, and cardiac function, underscoring its potential as a valuable intervention in clinical practice.However, prospective data are needed to further demonstrate the benefit of the combined therapy.trial (SBT).In this investigative cohort, the SBT procedure employs a T tube for direct disconnection from the ventilator.Upon successful completion of a 3-min SBT, patients autonomously breathe for an additional 30 min.Typically, individuals capable of tolerating this trial are deemed successfully weaned.However, given the specific focus on patients grappling with liberation challenges in this study, the spontaneous breathing duration is extended.Specifically, success in liberation is determined for patients who can sustain continuous spontaneous breathing for a prolonged period of 24 h.

Statistical analysis
Values were expressed as n (percentage, %) or mean ± SD.Four tests of Shapiro-Wilk test, Anderson-Darling test, Kolmogorov-Smirnov test, D' Agostino and Pearson test were used to test the normality of the data firstly.p values of the demographic and clinical characteristics for each group were derived from Mann-Whitney test.Chi-square test or Fisher's exact test was used for assessing distribution of observations or phenomena between two groups.Mann-Whitney test was used when the data were not normal.Unpaired t test with Welch's correction was used when the data were normal.Two-way ANOVA followed Turkey's multiple comparisons test was used to compare the differences between the groups with different time points.*p < 0.05, **p < 0.01, ***p < 0.001 and ns means no significance.

Fig. 1
Fig. 1 Flowchart of the work

Fig. 2
Fig.2Comparisons of the GCS score between the two groups before and after hyperbaric oxygen combined cabin ventilator treatment.Data were presented as mean ± SD showing all the data points.**p < 0.01, ***p < 0.001 and ns means no significance.Two-way ANOVA followed Turkey's multiple comparisons test

Fig. 3
Fig. 3 Comparisons of the PaO 2 (A), SaO 2 (B) and OI (C) between the two groups before and after hyperbaric oxygen combined cabin ventilator treatment.Data were presented as mean ± SD showing all the data points.*p < 0.05, **p < 0.01, ***p < 0.001 and ns means no significance.Two-way ANOVA followed Turkey's multiple comparisons test

Table 1
Demographic and clinical characteristics of patients who were successfully liberated (SL) and not successfully liberated (NSL) Values were expressed as n (percentage, %) or mean ± SD. p values for each group were derived from Mann-Whitney test.Chi-square test or Fisher's exact test was used for assessing distribution of observations or phenomena between two groups